Method for forming expanded base piles for uplift loads

ABSTRACT

This invention relates to a method for forming an expanded base pile capable of sustaining compression and uplift loads characterized by an elongated tensile element intimately connected to an expanded base and connected to a structure at the top, thereby to transfer the uplift load from the structure to the pile.

United States Patent Fuller 1 Aug. 22, 1972 [54] METHOD FOR FORMINGEXPANDED BASEPILES FOR UPLIFT LOADS [72] Inventor: Frank M. Fuller,Washington Township, Bergen County, NJ.

[73] Assignee: Raymond International, Inc., New

York, NY.

[22] Filed: Aug. 6, 1970 [21] Appl. No.: 61,759

[52] US. Cl ..61/S3.6, 61/5362 [51 Int. Cl. ..E02d 5/44 [58] Field ofSearch ..6l/50, 53.6, 53.62,'53.64-, 61/5366, 53.7

[56] References Cited UNITED STATES PATENTS 1,296,628 3/1919 Cooney..6l/5O X 2,438,729 3/1948 Upson et al ..6l/53.6

. X a y Q U 9 w Primary Examiner-David J. Williamowsky AssistantExaminer-David H. Corbin Attorney-Ward, McElhannon, Brooks andFitzpatrick 5 7] ABSTRACT This invention relates to a method for formingan expanded base pile capable of sustaining compression and uplift loadscharacterized by an elongated tensile element intimately connected to anexpanded base and connected to a structure at the top, thereby totransfer the uplift load from the structure to the pile.

17 Claims, 20 Drawing Figures PATENTED M1822 m2 SHEET 1 BF 4 5 E 3 v N 0O m A W M FOR UPLIFT LOADS This invention relates to new and improvedexpanded base piles and more particularly to such piles which arecapable of sustaining compression and uplift loads. The invention alsorelates to methods for forming such piles. The present invention isparticularly adapted, among other possible applications, for use intower structures, tank foundation flotation or earthpusher loads, forexample.

It has been found that both compression and uplift load capacities ofconcrete piles can often be increased by enlarging their lower ends. Forpurposes of sustain ing uplift loads, prior art pile arrangements wereformed by hammering a cage, in the form of reinforcing rods, into apreplaced expanded base to make a connection therewith and then fillingin and around the cage with concrete. Difficulties were encountered withsuch prior art techniques due to bending and deformation of the cage anddue to the tendency to form an inadequate connection with the base, andhence the base did not effectively contribute to the uplift resistanceof the pile.

The present invention involves a novel combination of features combinedin such a way as to afiord a very efficient solution to the difiicultiesencountered with the prior art, as will become apparent as thedescription proceeds.

The present invention, in one form thereof, involves a method of formingan expanded base pile capable of sustaining compression and uplift loadscomprising the steps of forcing concrete down into the bottom of apreformed hole in the earth with sufficient force so as to produce anexpanded base and thereafter placing an elongated tensile element intocontact with the expanded base, said element having laterally andlongitudinally extending spaced projections near the expanded base. Thenext steps in the method include, pouring concrete into the opening toextend up and form a column, and then expanding the column laterally inthe region of the base to form a secondary expanded base. According tothe invention, an additional step is included which comprisestransferring the uplift load from the structure to the pile. In one formshort dowels are connected to the top of the elongated tensile elementwhich usually consists of a steel pipe. In another form of the inventiona single pile is used under a load element and no pile cap per se isformed. Various means may be employed to make a positive connectionbetween the pile and the structure such as welding the dowels to thepipe, inserting reinforcing steel dowels in the concrete used to fillthe pipe and thus transferring tension loads through the bond, weldingthe main longitudinal steel for the reinforced concrete building columnsdirectly to the pipe pile, welding a collar around the top of the pipeto which building columns of structural steel could be bolted or weldedor embedding the collar itself in the concrete to form a part of thestructure, such as the floor of a tank, for example.

In another form, the invention involves a method of forming an expandedbase pile capable of sustaining compression and uplift loads comprisingthe steps of forcing concrete down into the bottom of a preformed holein the earth with sufficient force to produce an expanded base, thenceplacing an elongated rod-like tensile element into contact with saidexpanded base, and driving the lower end of said rod-like tensileelement into said base so that it extends up from the base in the holeto the top of the pile. In one form the method includes theadditional-steps of placing a small amountof A normal slump concrete ontop of the base, inserting a shell down into the hole to bear in thisfreshly placed concrete and on the expanded base, and thereafter fillingthe shell with concrete.

In still another form, there is provided a new and improved expandedbase pile for sustaining compression and uplift loads including anenlarged bulbous base under the surface of the earth, a concrete columnextending up from the base and a tensile element embedded in the baseand extending up the column. The tensile element has a laterally andlongitudinally extending portion in intimate contact with the base toprovide uplift load restraint. In addition, the tensile element isintimately connected to a structure at the top of the pile, thereby totransfer the uplift load from the structure to the pile.

According to my invention, in another form thereof, an expanded basepile includes a second bulbous base overlying the first bulbous base anda concrete column extending up from said bases and a tensile elementembedded at least in the second base and extending up the column. Thefirst bulbous base serves primarily to develop high load bearingcapacity in compression and the second bulbous base serves primarily toprovide the necessary uplift resistance.

There has thus been outlined rather broadly the more important featuresof the invention in order that the detailed description thereof thatfollows may be better understood, and in order that the presentcontribution to the art may be better appreciated. There are, of course,additional features of the invention that will be described more fullyhereinafter. Those skilled in the art will appreciate that theconception on which this disclosure is based may readily be utilized asthe basis for the designing of other structures for carrying out theseveral purposes of the invention. It is important, therefore, that thisdisclosure be regarded as including such equivalent constructions as donot depart from the spirit and scope of the invention.

Several embodiments of the invention have been chosen for purposes ofillustration and description, and are shown in the accompanyingdrawings, forming a part of the specification, wherein:

FIG. 1 is a vertical sectional view through a drive tube and mandreldisposed in a hole driven in the earth according to a first step of oneembodiment of the present invention;

FIG. 2 is a view similar to FIG. 1, but showing the mandrel forcing aplug from the lower end of the drive tube;

FIG. 3 is a view similar to FIG. 2, charge of concrete inserted in thehole;

FIG. 4 is a view similar to FIG. 3, but showing a mandrel insertedinside said drive tube for forcing the concrete to form an expandedbase;

FIG. 5 is a vertical, sectional view through a drive tube having a dryconcrete plug in the bottom end thereof and an internal drop weighttherein, according to another form of the present invention;

FIG. 6 is a view similar to FIG. 5, but showing the plug being forcedfrom the lower end of the drive tube;

but showing a FIG. 7 is a view similar to FIG. 6, but showing a chargeof concrete inserted in the hole;

FIG. 8 is a view similar to FIG. 7, but showing the charge of concreteformed into an expanded base;

FIG. 9 is a view similar to FIG. 8 andFlG. 4, but showing thearrangement after forming the base, and with a pipe, having strap meansat the lower end thereof, inserted in the drive tube;

FIG. 10 is an enlarged, perspective view showing details of U-shapedstraps attached to the lower end of the pipe;

FIG. 1 l is a view similar to FIG. 9, but showing an internal dropweight forcing a charge of concrete out to form a second expanded baseoverlying the first expanded base;

FIG. 12 is a view similar to FIG. 11, but showing the drive tubewithdrawn and the pipe filled with concrete, and a structure connectedto the pipe at the top thereof;

FIGS. 13 and 14 are enlarged, perspective views showing two additionalanchorage systems for the bottom of the pipe in the base;

FIGS. 15, 16, 17 and 18 are enlarged, perspective views showing threeadditional anchorage systems for connecting a structure to the top ofthe pipe;

FIG. 19 is a vertical, sectional view similar to FIG. 9, but showing arod-like tensile element being driven into the expanded base by slipweight means according to another embodiment of the invention, and

FIG. 20 is a vertical, sectional view similar to FIG. 19, but showingthe tensile element driven into the base, a shell inserted, the drivetube removed, the shell filled with concrete.

In the embodiment of the invention illustrated in FIGS. l-S, the methodof forming an expanded base pile capable of sustaining compression anduplift loads comprises the steps of driving a mandrel l2 and a drivetube 10, FIG. 1, having a dry concrete plug 14 at the bottom thereof,which serves to close the lower end of the tube, down into the earth 16into the bearing stratum, and then as seen in FIG. 2, driving the plugfrom the bottom of the tube while raising the tube from the hole, andthereafter placing a charge of zero slump concrete 18, FIG. 3, in thebottom of the drive tube 10. As seen in FIG. 4, the mandrel 12 serves todrive or force the concrete l8 downwardly and outwardly to form a firstexpanded base 21 having a cross section greater than that of the hole ordrive tube. This first or initial base is formed under very high drivingenergies to develop a pile with a high compression load bearingcapacity.

In the form of the invention illustrated in FIGS. -12, the method offorming an expanded base pile capable of sustaining compression anduplift loads comprises the steps of driving a drive tube 10, FIG. 5,having a dry concrete plug 14 at the bottom thereof, which serves toclose the lower end of the tube, down into the bearing stratum of theearth 16 by means of an internal drop weight 23, provided for thepurpose. The next step, as seen in FIG. 6, is driving the plug from thebottom of the tube while raising the tube from the hole, and thereafterplacing a charge of zero slump concrete 18, FIG. 7, in the bottom of thedrive tube 10. The charge of concrete 18 is driven downwardly andoutwardly,

from its position as seen in FIG. 7 to its position as seen in FIG. 8,to form a first expanded base 21 having a cross section greater thanthat of the hole or drive tube, by means of the internal drop weight 23.As pointed out hereinbefore, this first or initial base is formed undervery high driving energy to develop a pile with a high compression loadbearing capacity.

After forming the expanded base, by either the method illustrated inFIGS. 14 or by the method illustrated in FIGS. 5-8, the next step, asseen in FIG. 9, is lowering an elongated pipe 22 into the drive tube 10.As best seen in FIG. 10, the pipe 22 has steel strap means which, asillustrated, comprise a pair of U- shaped steel straps 24 welded to thebottom end thereof, as at 26. It should be noted that one U-shaped steelstrap could suffice and that the distance 27 which the straps projectbelow the end of the pipe varies depending upon the uplift loads to beresisted and upon other considerations. This distance could range from afew inches to several feet, for example. These straps are drivenpartially into the initial base 21 as at 25, FIG. 1 l, to form a bondbetween the concrete of the first and second base. Then a charge ofconcrete is placed in the pipe 22 and is based out as by means of theinternal drop weight 23 into or on top of the initial base 21 to form-asecond base 28 (FIG. 11) having full anchorage with the base 21. At thispoint, as can be seen, the base extends at or above the pipe bottom andis of greater cross section than that of the pipe 22. It will beappreciated that the initial base 21 is formed under very high drivingenergy to develop a pipe with high compression load bearing capacity andthe second base 18 is rammed out with less energy but still sufficientenergy to form an expanded secondary base to develop the upliftcapacity. The magnitude of the required capacity in uplift is generallymuch less than that required in compression. The size of the basesdepends on many factors such as the soil conditions, for example.Accordingly, it will be appreciated that the two bases have differentfunctions. The use of a pipe 22 for the tension element is particularlyadvantageous because, as seen in FIG, 11, the drop weight 23 operatesinside thereof and the pipe provides a smooth, continuous andunobstructed guide for the heavy drop weight. In addition, it should benoted that the concrete used in forming the secondary base 28 is not ofzero slump, but should contain enough moisture so that it can be forcedout around the straps 24 and compacted or rammed into the soil to formthe second expanded base as the drive tube is being withdrawn. As seenin FIG. 12, the drive tube 10 is thereafter withdrawn and the pipe 22 isfilled with concrete 30. The space 32 around the pipe 22 may be filledwith any suitable material depending upon such factors as the soilconditions, for example. For some soils this space may be filled in bythe soil itself, as the drive tube is withdrawn. In some cases the spacemay be filled with sand, other soil, or gravel, for example. In the formof the invention illustrated in FIG. 12, the pipe 10 is provided withports or openings 31 staggered along its length and around itscircumference so that when the concrete is poured into the pipe it flowsout the ports and fills any voids between the ground and the pipe. Aninternal vibrating rod 33 serves to assist the movement of this concreteout of the ports. This process assists in establishing lateral supportto the pile shaft. However, sufficient and continuous cross sectionalarea of steel is left in the pipe 22 to resist the necessary tensilestresses which is the primary purpose of the pipe.

Still referring to FIG. 12, the next step is welding short dowels 34 tothe top of the pipe to provide a connection transferring the upliftloads from a structure 36 to the pile. It will be appreciated that thepipe 22 serves a dual purpose. It acts as a tensile member, therebyreplacing the reinforcing bars used by prior art installations, and atthe same time provides a steel encasement for the shaft concrete, toprotect the concrete from detrimental ground pressures and movement,thereby replacing the shell used by prior art installations. The use ofthe pipe to replace both the shell and the reinforcing bars savesmaterial in addition to installation costs.

As seen in FIGS. 13 and 14, two other means are illustrated foranchoring the pipe 22 to the base. As shown in FIG. 13, two or moresteel L-shaped elements 35 are weldedto the bottom of the pipe 22, as at37. As seen in FIG. 14 two or more steel hooked elements 39 are weldedto the bottom of the pipe 22, as at 41.

Referring next to FIGS. 15, 16, 17 and 18, there are illustrated fouradditional means for anchoring the system to the top of the pile. Asseen in FIG. 15, two or more hooked or L-shaped steel elements 43 havetheir upper ends embedded in the concrete of the structure 36 and theirtwo lower ends are welded to the pipe 22, as at 45. As seen in FIG. 16,two or more hooked or-L- shaped elements 47 have their upper endsembedded in the concrete of the structure 36 and their lower endsembedded in the pile concrete 30. In FIG. 17 a steel collar 49 is weldedto the top of the pipe 22 and embedded in concrete or bolted to a columnbase plate 51. As seen in FIG. 18, a plurality of main columnreinforcement bars 53 of a structure are welded to the pipe 22, as at55. Accordingly, the embodiments of FIGS. 16, 17 and 18 show means forconnecting the top of the pile to a structure, thereby to transfer theuplift load from the structure to the pile.

In the embodiment of the invention illustrated in FIGS. 19 and 20, anexpanded base 21 is formed in the ground in the same manner as describedhereinbefore in connection with FIGS. 14 or 59. After forming the base21, the next step in this method includes driving the end of a rod-liketensile element 52 into the concrete base 21. The rod is of sufficientsize to take an uplift load, and it has a steel collar 38 welded theretoat a position located a short distance upwardly from the end thereof sothat a slipweight 40 may be employed to drive the bar into the base 21.Lifting lines 42 serve to lift the slip weight 40, as required. It willbe appreciated that this method of providing uplift resistance can beused either with a cased or with an uncased shaft. If a shell is to beused (to form a cased shaft) the next steps, FIG. 20, comprise placing asmall amount of normal slump concrete 44 on top of the base 21 and theninserting a shell 46 down into the hole to bear in the freshly placedconcrete and on the expanded base, and thereafter filling the shell 46with concrete 48. Thereafter, the steps include withdrawing the drivetube and filling the space around the shell 46 with any suitablematerial 50 depending upon the soil condition as discussed more fullyhereinbefore with respect to space 32, FIG. 12. The upper end of therod-like tensile element 36 is positively connected to the structurespecification, will be apparent to those skilled in the art to which theinvention pertains.

What is claimed and desired to be secured by Letters Patent is:

1. A method of forming an expanded base pile capable of sustainingcompression and uplift loads, said method comprising the steps offorming an opening down through the earth, forcing concrete down intothe bottom of said opening under sufiicient force to form a firstexpanded base having a cross-section greater than that of said opening,placing an elongated tensile element into contact with said firstexpanded base to extend up through said opening, said elongated tensileelement being hollow and having laterally and longitudinally extendingprojections near said first expanded base, placing a secondary charge ofconcrete in the bottom of said tensile element and basing it out on topof said first expanded base to form a secondary expanded base having across-section greater than that of said tensile element, said basingbeing continued until full anchorage is achieved between the tensileelement and the second base and pouring concrete to extend up as acolumn through said opening.

- 2. A method of forming an expanded base pile capable of sustainingcompression and uplift loads, said method comprising the steps ofdriving a drive tube down into the earth into the bearing stratum toform an opening down through the earth, placing a primary charge ofconcrete in the bottom of the drive tube, forcing the concretedownwardly and outwardly to form a first expanded base, lowering anelongated tensile element into said drive tube to a position at leastadjacent said first expanded base, said tensile element being hollow andhaving anchoring means on the bottom end thereof, placing a secondarycharge of concrete in the bottom of the tensile element and basing itout on top of the first expanded base to form a second expanded basehaving a cross-section greater than that of said tensile element, saidbasing being continued until full anchorage is achieved between thetensile element and the second base, withdrawing the drive tube andfilling the opening with concrete.

3. A method of forming an expanded base pile capable of sustainingcompression and uplift loads according to claim 2 wherein said primarycharge of concrete in the bottom of the drive tube is zero slumpconcrete and said secondary charge of concrete in the bottom of thetensile element is low slump concrete.

4. A method of forming an expanded base pile capable of sustainingcompression and uplift loads according to claim 2 wherein said anchoringmeans comprises at least one U-shaped strap fixedly connected to thebottom end of the tensile element.

5. A method of forming an expanded base pile capable of sustainingcompression and uplift loads according to claim 2 wherein said anchoringmeans comprises at least two L-shaped elements fixedly connected to thebottom end of the tensile element.

6. A method of forming an expanded base pile capable of sustainingcompression and uplift loads according to claim 2 wherein said anchoringmeans comprises at least two hooked elements fixedly connected to thebottom end of said tensile element.

7. A method of forming an expanded base pile capable of sustainingcompression and uplift loads according to claim 2 further comprising thestep of connecting anchoring means to the top of the tensile element totransfer the uplift load from a structure to the pile.

8. A method of forming an expanded base pile capable of sustainingcompression and uplift loads according to claim 7 wherein said structurehas a concrete portion adjacent the top of said tensile element, andwherein said anchoring means to the top of the tensile element comprisesat least two L-shaped elements embedded in said concrete portion.

9. A method of forming an expanded base pile capa-, ble of sustainingcompression and uplift loads according to claim 7 wherein said structurehas a concrete portion adjacent the top of said tensile element, andwherein said anchoring means to the top of the tensile element comprisesat least two hooked elements having their lower ends embedded in thepile concrete and their upper ends embedded in said concrete portion.

10. A method of forming an expanded base pile capable of sustainingcompression and uplift loads according to claim 7 wherein said anchoringmeans comprises a collar fixedly connected to the top of said tensileelement and connected to said structure.

11. A method of forming an expanded base pile capable of sustainingcompression and uplift loads according to claim 7 wherein said anchoringmeans at the top of the tensile element comprises a plurality of maincolumn reinforcement bars depending from said structure and fixedlyconnected to the upper end of said ten sile element.

12. A method of forming an expanded base pile capable of sustainingcompression and uplift loads according to claim 2 wherein said tensileelement is driven partially into said first expanded base, before saidsecond base is formed, to form a bond between said first and secondbases.

13. A method of forming an expanded base pile capable of sustainingcompression and uplift loads, said method comprising the steps ofdriving a drive tube down into the earth into the bearing stratum,placing a charge of zero slump concrete in the bottom of the drive tube,forcing the concrete downwardly and outwardly to form a first expandedbase having a cross-section greater than that of the drive tube,lowering an elongated pipe into said drive tube to a position at leastadjacent said first expanded base, said pipe having anchoring means onthe bottom end thereof, placing a charge of low slump concrete in thepipe and basing it out into and on top of the first expanded base toform a second expanded base having a cross section greater than that ofthe pipe, said basing being continued until full anchorage is achievedbetween said pipe and the second base, withdrawing the drive tube andfilling the pipe with concrete.

14. A method of forming an expanded base pile capable of sustainingcompression and uplift loads according to claim 13 wherein said pipe hasa plurality of portsstaggered along its length and around itscircumference, and further comprising the step of vibrating the concretein said pipe to promote its flow outwardly through said ports.

15. A method of forming an expanded base pile capable of sustainingcompression and uplift loads, said method comprising the steps ofdriving a mandrel in a drive tube having a dry concrete plug at thebottom thereof down into the earth to form a hole therein, driving theplug from the bottom of the tube while raising a portion of the tubefrom the hole, placing a charge of zero slump concrete in the bottom ofthe drive tube, forcing the concrete downwardly and outwardly to form afirst expanded base having a cross-section greater than that of the holeand drive tube, said first expanded base being formed under high drivingenergy to develop a pile with a high compression load bearing capacity,lowering an elongated pipe into the drive tube to a position at leastadjacent said first expanded base, said pipe having anchoring means onthe bottom end thereof, forming a secondary expanded base by placing acharge of low slump concrete in the pipe and basing it out into and ontop of the first expanded base until full anchorage is achieved betweensaid pipe and said secondary base and until the second base has acrosssection greater than that of the pipe, withdrawing the drive tubeand filling the pipe with concrete.

16. A method of forming an expanded base pile capable of sustainingcompression and uplift loads, said method comprising the steps ofdriving a drive tube having a dry concrete plug at the bottom thereofdown into the bearing stratum of the earth by means of an internal dropweight to form a hole extending down into the earth, driving the plugfrom the bottom of the tube while raising a portion of the tube from thehole, placing a charge of zero slump concrete in the bottom of the drivetube, driving said charge of concrete downwardly and outwardly to form afirst expanded base having a cross section greater than that of the holeand drive tube by means of an internal drop weight, said first expandedbase being formed under very high driving energy to develop a pile witha high compression load bearing capacity, lowering an elongated pipeinto the drive tube into contact with said first expanded base, saidpipe having anchoring means at the bottom end thereof, placing a chargeof low slump concrete in the pipe and then basing it out into and on topof the first expanded base by means of an internal drop weight withinsaid pipe to form a second expanded base having a cross-section greaterthan that of the pipe, said basing being continued until full anchorageis achieved between said pipe and second base, withdrawing the drivetube and filling the pipe with concrete.

17. A method of forming an expanded base pile capable of sustainingcompression and uplift loads, said method comprising the steps offorming an opening down through the earth, forcing concrete down intothe bottom of said opening under sufficient force to form a firstexpanded base having a cross-section greater than that of said opening,placing an elongated tensile element into contact with said firstexpanded base to extend up through said opening, placing a secondarycharge of concrete at the bottom of said tensile element and then basingit out into and on top of the first expanded base by means of aninternal drop weight guided by said tensile element to form a secondaryexpanded base having a cross-section greater than that of UN rrED rKTESipxTEN'r OFFICE CERTIFICATE CQ'RRECTIQN Patent No. 3,685,302 DatedAugust 22 1912 Inventor(s) Frank uller It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby COIIGC tGd as shown below:

Column 3, line 35, for, "5" read 4--;

Column 4, line 30, 'for "pi pe'f read pile-; Column 4 line 31, for "18"read 28-.

Signed and sealed this 9th day of January 1973.

(SEAL) Attest:

EDWARD MrPLLETCIIIER TR. ROBERT GOTTSCHALK Attesting OfficerCommissioner of Patents FORM PO-tOSO (0- I USCOMM-DC 603764 69 v.5,GDVERNNKNI PR NTING OFFICE: l969 O- bC-}34

1. A method of forming an expanded base pile capable of sustainingcompression and uplift loads, said method comprising the steps offorming an opening down through the earth, forcing concrete down intothe bottom of said opening under sufficient force to form a firstexpanded base having a cross-section greater than that of said opening,placing an elongated tensile element into contact with said firstexpanded base to extend up through said opening, said elongated tensileelement being hollow and having laterally and longitudinally extendingprojections near said first expanded base, placing a secondary charge ofconcrete in the bottom of said tensile element and basing it out on topof said first expanded base to form a secondary expanded base having across-section greater than that of said tensile element, said basingbeing continued until full anchorage is achieved between the tensileelement and the second base and pouring concrete To extend up as acolumn through said opening.
 2. A method of forming an expanded basepile capable of sustaining compression and uplift loads, said methodcomprising the steps of driving a drive tube down into the earth intothe bearing stratum to form an opening down through the earth, placing aprimary charge of concrete in the bottom of the drive tube, forcing theconcrete downwardly and outwardly to form a first expanded base,lowering an elongated tensile element into said drive tube to a positionat least adjacent said first expanded base, said tensile element beinghollow and having anchoring means on the bottom end thereof, placing asecondary charge of concrete in the bottom of the tensile element andbasing it out on top of the first expanded base to form a secondexpanded base having a cross-section greater than that of said tensileelement, said basing being continued until full anchorage is achievedbetween the tensile element and the second base, withdrawing the drivetube and filling the opening with concrete.
 3. A method of forming anexpanded base pile capable of sustaining compression and uplift loadsaccording to claim 2 wherein said primary charge of concrete in thebottom of the drive tube is zero slump concrete and said secondarycharge of concrete in the bottom of the tensile element is low slumpconcrete.
 4. A method of forming an expanded base pile capable ofsustaining compression and uplift loads according to claim 2 whereinsaid anchoring means comprises at least one U-shaped strap fixedlyconnected to the bottom end of the tensile element.
 5. A method offorming an expanded base pile capable of sustaining compression anduplift loads according to claim 2 wherein said anchoring means comprisesat least two L-shaped elements fixedly connected to the bottom end ofthe tensile element.
 6. A method of forming an expanded base pilecapable of sustaining compression and uplift loads according to claim 2wherein said anchoring means comprises at least two hooked elementsfixedly connected to the bottom end of said tensile element.
 7. A methodof forming an expanded base pile capable of sustaining compression anduplift loads according to claim 2 further comprising the step ofconnecting anchoring means to the top of the tensile element to transferthe uplift load from a structure to the pile.
 8. A method of forming anexpanded base pile capable of sustaining compression and uplift loadsaccording to claim 7 wherein said structure has a concrete portionadjacent the top of said tensile element, and wherein said anchoringmeans to the top of the tensile element comprises at least two L-shapedelements embedded in said concrete portion.
 9. A method of forming anexpanded base pile capable of sustaining compression and uplift loadsaccording to claim 7 wherein said structure has a concrete portionadjacent the top of said tensile element, and wherein said anchoringmeans to the top of the tensile element comprises at least two hookedelements having their lower ends embedded in the pile concrete and theirupper ends embedded in said concrete portion.
 10. A method of forming anexpanded base pile capable of sustaining compression and uplift loadsaccording to claim 7 wherein said anchoring means comprises a collarfixedly connected to the top of said tensile element and connected tosaid structure.
 11. A method of forming an expanded base pile capable ofsustaining compression and uplift loads according to claim 7 whereinsaid anchoring means at the top of the tensile element comprises aplurality of main column reinforcement bars depending from saidstructure and fixedly connected to the upper end of said tensileelement.
 12. A method of forming an expanded base pile capable ofsustaining compression and uplift loads according to claim 2 whereinsaid tensile element is driven partially into said first expanded base,before said second base is formed, to form a bond between said first andsecond bases.
 13. A mEthod of forming an expanded base pile capable ofsustaining compression and uplift loads, said method comprising thesteps of driving a drive tube down into the earth into the bearingstratum, placing a charge of zero slump concrete in the bottom of thedrive tube, forcing the concrete downwardly and outwardly to form afirst expanded base having a cross-section greater than that of thedrive tube, lowering an elongated pipe into said drive tube to aposition at least adjacent said first expanded base, said pipe havinganchoring means on the bottom end thereof, placing a charge of low slumpconcrete in the pipe and basing it out into and on top of the firstexpanded base to form a second expanded base having a cross sectiongreater than that of the pipe, said basing being continued until fullanchorage is achieved between said pipe and the second base, withdrawingthe drive tube and filling the pipe with concrete.
 14. A method offorming an expanded base pile capable of sustaining compression anduplift loads according to claim 13 wherein said pipe has a plurality ofports staggered along its length and around its circumference, andfurther comprising the step of vibrating the concrete in said pipe topromote its flow outwardly through said ports.
 15. A method of formingan expanded base pile capable of sustaining compression and upliftloads, said method comprising the steps of driving a mandrel in a drivetube having a dry concrete plug at the bottom thereof down into theearth to form a hole therein, driving the plug from the bottom of thetube while raising a portion of the tube from the hole, placing a chargeof zero slump concrete in the bottom of the drive tube, forcing theconcrete downwardly and outwardly to form a first expanded base having across-section greater than that of the hole and drive tube, said firstexpanded base being formed under high driving energy to develop a pilewith a high compression load bearing capacity, lowering an elongatedpipe into the drive tube to a position at least adjacent said firstexpanded base, said pipe having anchoring means on the bottom endthereof, forming a secondary expanded base by placing a charge of lowslump concrete in the pipe and basing it out into and on top of thefirst expanded base until full anchorage is achieved between said pipeand said secondary base and until the second base has a cross-sectiongreater than that of the pipe, withdrawing the drive tube and fillingthe pipe with concrete.
 16. A method of forming an expanded base pilecapable of sustaining compression and uplift loads, said methodcomprising the steps of driving a drive tube having a dry concrete plugat the bottom thereof down into the bearing stratum of the earth bymeans of an internal drop weight to form a hole extending down into theearth, driving the plug from the bottom of the tube while raising aportion of the tube from the hole, placing a charge of zero slumpconcrete in the bottom of the drive tube, driving said charge ofconcrete downwardly and outwardly to form a first expanded base having across section greater than that of the hole and drive tube by means ofan internal drop weight, said first expanded base being formed undervery high driving energy to develop a pile with a high compression loadbearing capacity, lowering an elongated pipe into the drive tube intocontact with said first expanded base, said pipe having anchoring meansat the bottom end thereof, placing a charge of low slump concrete in thepipe and then basing it out into and on top of the first expanded baseby means of an internal drop weight within said pipe to form a secondexpanded base having a cross-section greater than that of the pipe, saidbasing being continued until full anchorage is achieved between saidpipe and second base, withdrawing the drive tube and filling the pipewith concrete.
 17. A method of forming an expanded base pile capable ofsustaining compression and uplift loads, said method comprising thesteps of forming an opening Down through the earth, forcing concretedown into the bottom of said opening under sufficient force to form afirst expanded base having a cross-section greater than that of saidopening, placing an elongated tensile element into contact with saidfirst expanded base to extend up through said opening, placing asecondary charge of concrete at the bottom of said tensile element andthen basing it out into and on top of the first expanded base by meansof an internal drop weight guided by said tensile element to form asecondary expanded base having a cross-section greater than that of saidtensile element, said basing being continued until full anchorage isachieved between the tensile element and the second base, and pouringconcrete to extend up as a column through said opening.